Harwell Engineering Substantiation
| Contract: | Engineering Substantiation |
| Customer: | UKAEA |
| Scope: |
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| Details: |
The purpose of Engineering Substantiation is to underpin the safety arguments by demonstrating that sound engineering practices have been implemented and maintained throughout the facility lifetime, from design through construction to operations. The output from the process will be one or more Engineering Substantiation Reports (per facility or group of facilities or equipment). UKAEA requirement was for engineering support from recognised contractors over six nominated engineering disciplines: • Structural (including shielding, seismic etc.) • Vessels and pipework (including pressure vessels to ASME codes) • Ventilation • C&I (including electrical supplies) • Services (including water, utility services, site alarm response, drainage) • Mechanical handling (including cranes, manipulators, conveyors, gloveboxes/shielded cells, flasks etc.). Typical facilities to be assessed were: • B220 Radiochemical Laboratories (α gloveboxes and shielded cells) • B462 Solid Waste Store (monitoring, decontamination, size reduction, waste drum packaging and storage) • B459 High Activity Workshop (α gloveboxes, high active process and maintenance areas, MSM refurbishment) • B466 Pond (cobalt storage pond, handling equipment) • Material Test Reactors (DIDO, PLUTO, GLEEP, BEPO decommissioned reactors currently in care and maintenance phase) • Site Liquid Effluent Treatment Plant (receipt of liquid discharges for treatment and disposal) • Radioactive Materials Transportation (packaging, flasks, waste drums, on-site transport procedures). NES were successful in being awarded the mechanical handling discipline. The requirement was for the nominated company to have a dedicated team of engineers including a lead expert (part time site based) supported by a practitioner (site based) and a supervised practitioners (site based). Additional supervised practitioners were to be introduced as per the demand to suit the programmed workload. Furthermore, it was anticipated that one discipline will take the lead role on each facility – dependent upon the scope required. NES had the lead discipline role on four of the seven facilities being addressed. The process that was followed was specified by UKAEA and structured as five distinct stages: • Familiarisation • Desktop safety review • Reconciliation and classification • Plant walkdown • Substantiation of equipment. Familiarisation – obtain and high-level review source information consisting of existing safety reports, fault schedules, drawings and calcs, operational reports/UNOR’s, technical specifications, O&M instructions etc. During this stage early interaction between the facilities, safety case authors, and the engineering substantiation teams was required. Desktop safety review – detail review of the fault schedule identifying safety significant systems and sub-systems (SSC’s) and the continuing challenge to the required functionality and safety significance assigned by the safety case author. This stage of the process was closed-out with an agreement between the facility, safety case author and the engineering substantiation team on the extent of which SSC’s were to be substantiated. Reconciliation and classification – the process continues where the engineering substantiation team reviewed the hazard analysis and compared it with the engineering requirement or implementation/safety function. Any areas of conflict are discussed with the safety case author and the facility ATO holder such that an agreed consolidated approach and understanding is obtained (equipment classifications must be confirmed). Other than class 4 items there must be a consolidation process between the desktop exercises and walkdowns, wherein the safety case engineer, plant operators and engineering substantiation team reviewed and confirmed their findings. This agreement formed the basis of classification which in turn determines the extent of substantiation and reporting required. Class 1 equipment required extensive investigation and substantiation/reporting whereas a class 4 plant item simply required a walkdown sheet. Plant walkdown – this involved a visual inspection of the safety-related plant and structures to ascertain the existing condition and status, and to confirm the scope and extent of the SSC’s against the preliminary data output from the desktop review. It also allowed the team to identify any interactive threats to the SSC’s. Compliance with good practice for industrial health and safety and ergonomics was picked up. The plant operators and maintenance staff accompanied the walkdown and support the engineering substantiation team in gaining a greater understanding of the history of the equipment. Substantiation of equipment – having established the definitive list of SSC’s each item has to be individually assessed according to its state of repair, downtime, ageing effects, operating conditions, capability of performing its intended safety function etc. The assessment was made against current standards e.g. BS, NF, EDSP’s, ASME, AECP’s, ISO, and statutory legislation (LOLER, PUWER etc.). The engineering substantiation team was empowered to use its expert judgement to select the appropriate standards for the evaluation. The significant outcome of the engineering process was to determine whether the plant item is fit for purpose or not. The format of the report required the inclusion of key areas of investigation, stipulated by UKAEA but gave the team scope to identify shortfalls in the existing substantiation/design against its safety function or applicable standard, and included for recommendations to mitigate the shortfall. Finally, all engineering substantiation reports were issued for independent technical assessment (ITA) and the concluding report presented to the facility and safety case author for feedback of the areas in need of improvement. Where necessary, NES also produced base information where it does not exist for any associated plant item i.e. BS2573 calcs for cranes etc. including seismic analysis, impact withstand capability for dropped flask scenarios, undertaking ITA, undertaking site surveys and produced equipment engineering drawings etc. All of the engineering information formed an integral part of the audit/evidence trail required during the process. Note that all of this ‘additional support’ work was considered to be extra to the basis engineering exercise and was performed in the NES offices at Wolverhampton following initial search for input documentation etc. |